1899] DEVELOPMENT OF HOLDFASTS OF FLORIDE 255 
___ The species remaining for consideration belong to the Cera- 
_ -miacee. Cultures of Spermothamnion Turneri Aresch. were unsuc- 
cessful, only one healthy plantlet having been obtained. It 
developed two small disks, the one a terminal primary holdfast, 
the other a secondary structure arising from one of the middle 
wllsofthe filament (P/. XX//L, fig. gz). As Strémfelt has pointed 
out, the mature rhizoids are short, unicellular, unbranched 
_ ogans, terminating in a lobed disk in which delicate threads of 
_ protoplasm can be traced (Pl. XXIII, figs. 42, 43). The rhizoids 
ue especially abundant near the base of the plants, but, as is 
well known, any cell of a procumbent branch may give rise to 
_ these simple bodies. Now and then, an ordinary branch of the 
_ ftond produces at its apex a much-lobed twisted disk, which 
- tlosely embraces a neighboring branch as a tendril would a sup- 
| port (PL. XXII, jig. 40). ; 
Very few spores of Griffithsia Bornetiana Farlow germinated, 
and the resulting plantlets were short-lived. It is, therefore, 
possible to describe each step in the development of the hold- 
Gow Two unequal cells arise from the first division (teat fig. 
pe * Monosiphonous filament composed of rather globose 
4 cells is formed, the basal cell of which elongates and becomes 
: the root-cell (text fig. 2). The structure of mature holdfasts 
Mould lead one to Suppose that the primary root-cell divides 
p eedly, forming a broad spreading mass of large-celled 
t oY Ep tous tissue. The holdfasts of a young plant 
F thes ® 4 small piece of bone (teat fig. 3) and of older 
/} g owing on Zostera marina L. differed only in size, that of 
2 a! being very large with an abundance of adventitious 
| Hac. gs from its margin. Strémfelt (8) places the 
ae thsia with Ceramium and Callithamnion in a group 
: guish 
‘ Mina” Eatations were seen. The cells of the holdfasts are 
ay :.. and have very dense granular contents, prob- 
oR tlie . bs Supply of reserve food-material. 
“y allied genus, Callithamnion, differs greatly from 
